Anti-whaling group Sea Shepherd's ship is moored in Sydney in August 2013.

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An anti-whaling group says it split up Japan's fleet and chased it out of the Antarctic zone

"Within a day and a half, we have the entire whaling fleet in disarray," an activist says

Japan says the whaling ships are still in the Southern Ocean and the hunt continues

Environmental groups clash each year with Japan's whaling vessels

Environmental activists have declared an early success at the start of their annual high seas showdown with Japanese whalers in Antarctic waters.

The anti-whaling group Sea Shepherd Australia said its ships had split up the Japanese fleet in the Southern Ocean and chased it out of the main Antarctic zone.

"The whale poaching fleet is scattered and currently not hunting whales," Sea Shepherd said in a statement Monday.

But Japanese authorities say the hunt is still on.

Japan's fleet carries out an annual whale hunt despite a worldwide moratorium, taking advantage of a loophole in the law that permits the killing of the mammals for scientific research. Whale meat is commonly available for consumption in Japan.